Method for forming a double curvature connector



June 27, 1967 Q. BERG 3,327,372

METHOD FOR FORMING A DOUBLE CURVATURE CONNECTOR Filed June 30, 1964 X4 mnl.

INVENTOR.

United States Patent 3,327,372 METHGD FOR FORMING A DOUBLE CURVATURE CONNECTOR Quentin Berg, Berg Electronics, Inc, 142 Reno St., New Cumberland, Pa. 17070 Filed June 30, 1964, Ser. No. 379,190 1 Claim. (Cl. 29-15555) This invention relates to current conducting terminals of the tuning fork type and has particular reference to a unique and simple method of making such terminals which makes it possible to efficiently produce uniformly high quality terminals substantially better in performance than terminals of the type produced in accordance with conventional techniques. With conventional techniques it is difficult and expensive to get uniformly smooth contact surfaces.

Connectors of this type are used very extensively in computers and data processing machines. The cost of these connectors is an important factor. Quality is of even greater significance because the resistance of the electrical joints must be uniform and constant in use. The problem of efficiently producing high quality terminals is complicated by the extremely small size of these connectors and the close spacing of the contact surfaces, which make it diflicult to obtain uniformly good contact surfaces. It has been found that connectors produced in accordance with the method herein disclosed have uniformly smooth contact surfaces and perform considerably better after repeated use and salt spray tests than similar connectors made in accordance with conventional methods.

A principal object of the invention, therefore, is to provide an efiicient and improved method of making connectors of the tuning fork type.

Another object of the invention is to provide a simple and efficient method of making uniformly high quality connectors with doubly curved contact surfaces.

Other and further objects of the invention will be apparent from the following description and claim and may be understood by reference to the accompanying drawing, which by way of illustration shows a preferred embodiment of the invention and what I now consider to be the best mode of applying the principles thereof. Other embodiments of the invention may be used without departing from the scope of the present invention as set forth in the appended claim.

In the drawings:

FIG. 1 is an enlarged view of a tuning fork connector embodying the invention;

FIG. 2 is a similar view with a blade inserted between the contacts;

FIG. 3 is an enlarged sectional view taken along the line 33 of FIG. 2;

FIG. 4 is a fragmentary plan view of a metal blank illustrating certain steps in the method of making the connector; and

FIG. 5 is a cross sectional view illustrating the coining step of the method.

The tuning fork type of connector as illustrated is preferably made from a sheet of copper bronze stock and, as illustrated in FIG. 1, includes a wire wrap pin 11 at one end and a bifurcated connector 12 at the other end which includes a pair of lateral contacts 14 disposed at the ends of flexible arms 16. The contacts 14 and the arms 16 of connectors as commonly used are spaced about .020 inch for the reception therebetween of a blade 18, the sides of which are engageable with the contacts 14 so as to establish an electrical contact therebetween, as illustrated in FIGS. 2 and 3.

It is common to mount a series of connectors 10 in 3,327,372 Patented June 27, 1967 "ice parallel in a block in which the connectors 12 are recessed and secured in the block and in which the pins 11 project from the block so as to provide what might be termed a multiple disconnect or coupling.

The edge 20 provides a shoulder for seating against a corresponding shoulder in the block, and the triangular shaped projection 22 on one of the arms 16 is engageable with a part of the block so as to limit the deflection of one of the arms 16. However, the arms 16 need to be free to yield somewhat since the normal spacing between the contacts 14 is less than the thickness of the blade 18 whereby the contacts 14 are resiliently held in contact with the opposite sides of the blade 18. The actual connector as illustrated in FIG. 1 has an overall length of about 1.5 inches.

The invention herein disclosed is concerned with making these connectors more efiiciently and uniformly than is possible with conventional methods. An unexpected advantage of the method resides in the fact that the contact surfaces produced in accordance with this method are smoother and perform considerably better than contact surfaces of connectors made in accordance with conventional techniques.

The method essentially consists of performing a series of die operations on a blank 24 of sheet metal so as to form by a shearing operation an elongated hole 30 having areas 32 at the opposite sides of the hole bounded by curved edges generally corresponding to the contacts 14, enlarging the hole as indicated at 34 by shaving the curved edges 35 so as to eliminate the rough break in the metal which occurs at the end of the shearing operation and form the areas 32 to an intermediate size, burnishing the curved edges to a smooth finish, and then applying met-a1 deforming pressure by a coining operation to the opposite sides of the areas 32 simultaneously to both of the contacts as illustrated in FIG. 5 so as to displace metal outwardly at the curved edges so as to form the areas to their finished size and make the edges thereof doubly curved as indicated at 36. The shaving removes about .003 inch of metal from each of the curved edges. Thereafter the connector is formed from the blank through one edge of the hole as indicated at 40 so as to form the connector as illustrated in FIG. 1 with the arms 16 and the pin 11 and so that the contacts 14 are free to yield or separate when a blade is inserted therebetween as illustrated in FIG. 2. The punched connector is then separated from the stock as indicated at 42.

The dies for carrying out the process may be conventional punches of suitable form to produce the shapes illustrated, and the burnishing may be performed by the edge of a shaving tool which shaves or trims the edges 35 of the areas to the desired curvature. The tools can be mounted in a suitable reciprocating press which will make two or more connectors at a time. The shaving operation eliminates the ragged die break which occurs in the metal at the end of a shearing operation and the burnishing operation leaves a smooth surface on the edge 35 free of burrs.

The coining step illustrated in FIG. 5 extrudes the metal of the areas 32 at the curved edges 35 as illustrated so as to form the doubly curved surfaces 36. These surfaces 36 are smooth. After the connectors 10 are separated from the blank they are suitably plated, for example with a very thin gold or tin lead solder coating over nickel. This coating is of a thickness of the order of .000003 to .000020 inch thick. The coining operation leaves a smooth curved mating surface for the blade and provides a smooth surface for the subsequent plating, and hence minimizes wear on the plated surfaces of both contacts. Since the alignment between the pin 18 and the contact 10 will vary, the doubly curved surfaces 36 will provide uniform contact engagement between the pin 18 and the contacts 14, and as the process produces a smooth surface on the contact surfaces 36 the resistance of the joint should remain constant.

While I have illustrated and described a preferred embodiment of my invention, it is understood that this is capable of modification, and I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes and alterations as fall within the purview of the following claim.

I claim:

That method of making a tuning fork electrical connector having laterally extending contacts projecting toward each other and closely spaced double curvature contact surfaces facing each other for engagement with the opposite sides of a blade inserted therebetween which comprises: punching a hole in a sheet metal blank so as to form areas at the opposite sides of the hole bounded by single curved edges perpendicular to the plane of the sheet generally corresponding in shape to one are of curvature of the contacts, enlarging said hole to remove the rough punch break and shaving such curved edges so as to form said contact areas to an intermediate size, burnishing such single curved edges to a smooth and uniformly platable finish, applying metal deforming pressure to the opposite sides of said areas of both of said contacts so as to displace metal outwardly of each curved edge and toward the other of said curved edges so that such edges are doubly curved, and severing said connection from said blank through one edge of said hole so that said contacts are free to yield when a blade is inserted therebetween.

References Cited UNITED STATES PATENTS 2,377,558 6/ 1945 Johnson 7860 2,460,231 1/1849 Matthysse 39947 2,502,253 3/1950 Fox 33947 3,189,703 6/1965 Chapin et a1 200-67 3,202,122 8/1965 Bedford 2915S.55 X 3,299,493 1/1967 Gehrt et al. 29155.55

JOHN F. CAMPBELL, Primary Examiner.

R. W. CHURCH, Assistant Examiner. 

